1. Field of the Invention
The present invention relates generally to cathode ray tube (CRT) funnels. The present invention relates more specifically to CRT funnels in a CRT envelope extending between a generally conical neck section and a generally rectangular, flat, skirtless, face panel.
2. Description of the Related Art
The assignee of the present invention is known to manufacture a flat tension mask (FTM) CRT in a 14 inch diagonal screen size, such as designated by Model No. ZCM 1492. CRT's are evacuated envelopes, which must withstand certain pounds per square inch (p.s.i.) pressure to be considered safe. Because FTM CRTs are constructed with the funnel section attached directly to a face panel which is flat, discontinuity stresses occur at the face panel-to-funnel junction as a result of atmospheric loading on the evacuated tube. As screen sizes and aspect ratios of the screens increase, discontinuity stresses increase for a given wall thickness of panel and funnel and the CRT can withstand less pressure loading. The obvious solution is to increase the mass of the CRT envelope components but numerous drawbacks are associated with this solution.
It is therefore an object of any proper funnel design to decrease these discontinuity stresses, thus enabling the CRT funnel to withstand atmospheric loading at a safe level without undue costs in terms of increased CRT envelope materials and increased processing times.